JPS6215622A - Pressure-sensitive coordinate input device - Google Patents

Abstract

PURPOSE:To minimize the error of the position information and to obtain the accurate information by sampling the voltage corresponding to a pressure applied position by plural times in a prescribed time and calculating the average of the sampled voltage data. CONSTITUTION:The voltage data V1-V4 sampled by the sampling signal 12a are stored in a memory 15. An adder 16 reads those data V1-V4 out of the memory 15 and calculates the sum S of these data. Then, a divider 17 divides the sum S by the sampling frequency N and supplies the result of this division to a control part in the form of an output 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pressure-sensitive coordinate input device, and more particularly to a pressure-sensitive coordinate input device that detects coordinate information of a pressed position due to pressure applied by a writing instrument. .

(Prior Art) The basic configuration of a tablet in a conventional coordinate input device is shown in FIG. The tablet shown in the figure has a high-resistance film 2 coated on an insulating substrate 1, a low-resistance film 3 coated on the surrounding four sides, and a pressure-sensitive rubber 4 placed on the resistance films 2 and 3. A flexible film sheet 5 having a conductive film formed on the back surface serving as an electrode is provided on the upper part of the electrode.

The operation is performed in the x and y directions in a time-division manner, and when determining the X coordinate, a voltage is applied in the X direction. When applying voltage in the X direction, apply voltage E (v) to points B and C, and apply 0 [v] to the fish oil.
), the entire low-resistance film (3) BC becomes E (V
), and the resistance is low [3] The entire AD is 0 [V]
Takes the neighboring value. In addition, the low resistance film (3%B) and the low resistance film (3) DC have a potential gradient from 0 [v] to E (v'), and the high resistance driven by the low resistance film (3) BC and AD. Since the membrane 2 also has a potential gradient from 0 [V] to E (:V), by making the resistance distribution inside each resistor 2.3 uniform, regardless of the magnitude of the resistance value, the double-folding antibody The potential gradients become almost equal, and the disturbance in the potential becomes very small.

Next, when calculating the X coordinate, apply a voltage in the X direction, but apply voltage ECv to points A and B and voltage 0 [v] to points C and D in the same way as when calculating the X coordinate. , forming a potential gradient in the X direction.

When a voltage is applied alternately in the X direction and the X direction and a writing instrument such as a pencil is pressed from above the paper placed on the film sheet 5, the potential of the high resistance film 2 at the pressing point changes to the pressure sensitive rubber. 4 to the conductive film formed on the back surface of the film sheet 5. This potential is converted in synchronization with the timing of drive voltages applied alternately in the X'1 direction, and as a result, xy coordinate values on the tablet are obtained.

FIG. 5 is a diagram showing an equivalent circuit of the voltage input section in the above case. In the same figure, 6 is a high resistance film 2 and a low resistance film 3.
is the equivalent resistance of the entire resistive film including 7 is the equivalent resistance of the pressure-sensitive rubber 4, and its vertical resistance value changes from several tens of ohms to several tens of megaohms depending on the pen pressure. 8 is a distributed capacitance existing between the conductive film of the film sheet 5 and the resistive films 2, 3, etc.

Reference numeral 9 denotes an impedance converter for keeping the voltage input section at high impedance, and outputs the position voltage output to the 0 point in the figure to the A/D converter 10.

10 converts the position voltage from the impedance converter 9 into A/D
This is a φ converter that converts and outputs. Reference numeral 11 controls the opening and closing of a switch SWI, which will be described later, as well as a voltage switch f IJ.
This is a timing controller that controls the timing of the A/I conversion in the A/I converter 10. 1
2 is from the timing controller 11 to the A/I) converter 1
(See FIG. 6). 13 is a noise source generated by the human body, and 14 is a stray capacitance existing between the human body and the conductive film of the film sheet 5. In addition, E is a battery for applying voltage to the resistive film,
Swl is a switch that is controlled by the timing controller 11 and applies voltage to the resistive film, and originally there are multiple switches x
, a voltage is applied in the X direction, but one switch is shown in FIG. 5 to simplify the explanation.

In this equivalent circuit, when pressing an arbitrary point on the high-resistance film 2, that is, point 0 in FIG.
When closed, the voltage at the 0 point increases as the distributed capacitance 8 is charged via the resistor 6.7, and finally becomes the position potential at the 0 point in the potential distribution of the resistor 6. That is, resistance 6
Assuming that the equivalent resistance for charging the distributed capacitance 8 of the resistor 7 is R1, and the value of the distributed capacitance 8 is C8, the voltage waveform va becomes exponential with a delay of time constant r=R-03, as shown in ■ in Figure 6. Although it rises functionally, it becomes stable during the time T when SWI is closed, and is taken into the position detection section by the sampling timing signal 12 output from the timing controller 11.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional device, when a part of the human body touches the tablet while writing, the human body generates noise induced by the touch and the film sheet 5. is guided to the film sheet 5 via the stray capacitance of . And an impedance converter 9 connected to the film sheet 5
Since the high resistance film 2 and the high resistance film 2 both have high impedance, the induced noise voltage cannot be ignored, and this noise voltage is directly added to the detected voltage from the high resistance film 2. As a result, in a device that detects the position coordinates of the writing position by sampling this detection voltage, minute voltage fluctuations caused by noise induced by the human body directly result in errors in coordinate information, making it impossible to obtain accurate coordinate information. There is a problem.

The present invention is intended to solve these problems, and has the advantage of minimizing positional information errors caused by microvoltage fluctuations caused by human body-induced noise, etc., and obtaining accurate positional information of the writing position. The purpose of this invention is to provide a coordinate input device.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a resistive film, a drive device for applying voltage to the resistive film, a pressure sensitive rubber layered on the resistive film, An electrode sheet having a conductive film and laminated on the pressure-sensitive rubber, and a voltage corresponding to a pressure position appearing on the electrode sheet due to pressure applied by a writing instrument are detected in a time-sharing manner, and the detected voltage is detected. In a pressure-sensitive coordinate input device equipped with a detection device for digitizing and outputting,
The detection device is characterized in that it has the following two means.

The first means samples the voltage corresponding to the pressurized position multiple times at predetermined time intervals. The second means is the first
Calculate the average of the voltage data sampled by the means.

(Function) According to the present invention having the above configuration, the first means obtains voltage data by sampling the voltage at a plurality of sampling timings within the time when the voltage is applied to the resistive film. Then, all of the voltage data are added together, and the sum is divided by the number of sampling times to calculate the average of the voltage data. By the above-described processing operation, it is possible to subdivide the human body-induced noise contained in the voltage applied to the resistive film to minimize the influence on positional information, and to eliminate the above-mentioned conventional problems.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the same figure, the same reference numbers as in FIG. 5 indicate the same elements,
As a different element, 12a is a timing controller 1
1 is a voltage sampling timing signal supplied to the φ converter 10, and 15 is a voltage application time T at the A/D converter 10.
16 is an adder that reads each voltage data sampled multiple times within the voltage application time T and adds them together; 17 is an adder 16; A divider 18 calculates the average value of the voltage data by dividing the sum of the voltage data calculated by the number of samplings, and 18 is an output indicating the calculation result of the divider 17. is supplied to a control section (not shown).

FIG. 2 is a diagram showing the sampling timing signal and voltage waveform in this embodiment, and FIG. 3 is an enlarged diagram of the voltage waveform of the sampled portion in FIG. 2. The operation of this embodiment will be explained below based on FIGS. 1, 2, and 3. The voltage waveform v8 shown in FIG. 2 corresponds to the signal waveform at the 0 point or the input part of the ψ converter 10 in FIG. The waveform is stable within the voltage application time T, that is, the voltage application time T. Further, the sampling timing signal 12a is the sampling timing t4 of the conventional example shown in FIG. 6 at the last part of the stable part of the voltage waveform v8.
In addition, a predetermined time ttytztts immediately before this is added, and the stable part of the voltage waveform v8 is sampled a total of four times. However, the sampling timing ta is output after a sufficient period of time has elapsed from the rise of the voltage waveform V until it becomes sufficiently stable.

Next, in FIG. 3, 8 to v4 are voltage data at sampling timings t1 to t4. First, when history 1 closes, the voltage waveform va rises and reaches a stable portion, SW1 is closed, and after a predetermined period of time has elapsed, the sampling operation is started.

Then, the voltage data V-v4 sampled at sampling timings t8-t4 are stored in the memory 15. Next, the adder 16 receives the voltage data V from the memory 15,
Read ~v4 and sum S=v 1 + V 2 + V
Calculate s + v4. Then, the divider 17 divides the addition result S by the number of samples N (N=4 in this embodiment), and the result is V=S/N=(■1+v2
+v, +v4)/4 is supplied as an output 18 to a control section (not shown).

Therefore, as described above, the voltage data V, ~v4 includes errors caused by minute voltage fluctuations due to human body induced noise, etc., as explained in the conventional example, but the sampling performed after the voltage data is stabilized. The error can be minimized by calculating the average value V by sampling a plurality of times.

In the above embodiment, the memory 15, adder 16, and divider 17 are shown as separate elements, but they can also be configured using a single microcomputer, and a control section (not shown) at a subsequent stage may be used. It may be configured by a computer.

(Effects of the Invention) As described above, according to the present invention, it is possible to minimize errors in position information caused by minute voltage fluctuations due to human body-induced noise, etc., and to obtain accurate position information of the writing position. It is possible to provide an excellent coordinate input device that can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a sampling timing signal and voltage waveform in this embodiment, and FIG. 3 is an enlarged view of the voltage waveform of the sampled portion in FIG. 2. , FIG. 4 is a block diagram showing the basic structure of the tablet, FIG. 5 is a block diagram showing the circuit structure of a conventional voltage input section, and FIG. 6 is a diagram showing the sampling timing signal and voltage waveform in the conventional device. . 1... Insulating substrate, 2... High resistance film, 3... Low resistance film, 4... Pressure sensitive rubber, 5... Film sheet), 6.
7...Resistor, 8...Distributed capacitance, 9...Impedance converter, 10...NΦ converter, 11...Timing controller, 42, 12a...Sampling timing signal, 13...・Noise source, 14... Stray capacitance, 15... Memory, 16... Adder, 17.
...Divider, 18...How to get it. Patent Applicant: Oki Electric Industry Co., Ltd. Agent, Patent Attorney: Megumi Yamamoto - G Shokuto Hatsu > J Lindszung Lr - Moxibustion Spring Corner 1
Ceremony Sun (National Policy 3 Charts Tablet Firewood 19 Flashes 4th Chart 1 Shiba (41 Manpower 1 Race/■1 Furnace 11ρChar) b1
Figure 5 Figure 6

Claims (1)

[Scope of Claims] A resistive film, a drive device that applies voltage to the resistive film, a pressure-sensitive rubber laminated on the resistive film, and an electrode having a conductive film and laminated on the pressure-sensitive rubber. A pressure-sensitive coordinate system comprising a sheet and a detection device that time-divisionally detects a voltage corresponding to a pressure position that appears on the electrode sheet due to pressure applied by a writing instrument, and digitizes and outputs the detected voltage. The input device is characterized in that the detection device includes means for sampling the voltage corresponding to the pressurized position multiple times at predetermined time intervals, and means for calculating an average of the voltage data sampled by the means. A pressure-sensitive coordinate input device.